The present invention relates to an airbag apparatus. More specifically, the present invention relates to an airbag including a vent hole for absorbing an impact and a constraining device for constraining discharge of gas from the vent hole.
A technique to provide a vent hole in an airbag for allowing gas to discharge from the inside of the airbag via the vent hole to absorb an impact applied to a passenger or the like of a vehicle when the passenger of the vehicle or the like crashes into the inflated airbag is known to those in the field of airbag apparatus.
Japanese Unexamined Patent Application Publication No. 2000-16228 discloses an airbag in which the vent hole is covered by the a lid member until the gas pressure in the interior of the airbag reaches a predetermined pressure and, when the pressure exceeds the predetermined pressure, the lid member is pushed and opened by the gas pressure thereby opening the vent hole.
In the same document, an airbag for a driver's seat for a vehicle is exemplified. The airbag in the same document is formed by stitching two circular sheet members (panels) together along the peripheries thereof, which defines a single chamber. A vent hole is provided on a sheet member on the side opposite from the vehicle passenger side of the airbag, and a lid member is provided so as to cover the vent hole.
In the airbag of the same document, when the airbag is inflated, the vent hole is covered by the lid member and the gas is constrained from being discharged from the vent hole until the gas pressure in the interior of the airbag reaches the predetermined gas pressure, the pressure in the interior of the airbag is quickly increased to a high pressure, and hence the airbag is quickly deployed.
When the gas pressure in the interior of the airbag exceeds the predetermined pressure, the lid member is pushed and opened and the vent hole is opened. Therefore, in a case in which the vehicle passenger crashes into the inflated airbag, gas is flowed out from the interior of the airbag via the vent hole, and an impact applied to the vehicle passenger is absorbed.
In the 2000-16228 publication, when the pressure in the interior of the airbag is increased to a high level equal to or higher than the predetermined pressure, there may be a case in which the vent hole is opened, even in a stage before the passenger crashes into the airbag. In such circumstances, gas is needlessly discharged from the vent hole and may be detrimental to the purpose of protecting the passenger.
Accordingly, an object of the present invention is to provide an airbag and an airbag apparatus in which a vent hole is maintained in a closed or a slightly opened state until a passenger crashes into the airbag and the vent hole is opened or brought into a largely opened state when the passenger crashes into the airbag.